The overall objectives of this project are to develop radionuclide scanning methods for the early diagnosis, localization and size measurement of acute myocardial infarcts in patients admitted to the coronary care unit; to develop methods for evaluating the effects of interventions to protect ischemic myocardium and to reduce infarct size that can be easily and safely applied to coronary care unit patients, and further to evaluate these methods in patients; to develop a radionuclide technique for accurately quantitating abnormalities in left ventricular wall motion and to apply this technique to attempt to distinguish between reversible ischemia, acute infarction and old scar tissue in an individual patient as well as to evaluate the long term benefits of interventions in patients with acute infarcts; and, finally, to evaluate the isolated rabbit heart preparation for the screening and cellular localization of myocardial imaging agents.